Flame tube having telescoping walls with fluted ends to admit air



Jan. 2 0, 1953 D MCCARTHY ETAL 2,625,792 I ING TELESCOPING WALLS FLAME'ruE HAV WITH FLUTED ENDS TO ADMIT AIR' Filed Sept. 2, 1948 4Sheets-Sheet l i 4 Amer/me! DEN/S M ammy ,4. a I? SM/TV Jan. 20, 1953 D.M CARTHY ET AL 2,625,792

FLAME TUBE HAVING TELESCOPING WALLS 7 WITH FLUTED ENDS TO ADMIT AIR 4Sheets-Sheet 2 Filed Sept. 2. 1948 M ra/me; 051w: MtAkT/IY A. a. E sM/mE Jan. 20, 1953 MccARTHY ETAL 2,625,792

- FLAME TUBE HAVING TELESCOPING WALLS WITH FLUTED ENDS TO ADMIT AIRFiled Sept. 2, 1948 4 Sheets-Sheet 3 E WWW Ami-n Jan. 20, 1953 D.MCCARTHY ET AL 2,625,792

FLAME TUBE HAVING TELESCOPING WALLS WITH FLUTED ENDS T0 ADMIT AIR 4Sheets-Sheet 4 Filed Sept. 2. 1948 HL GO TM R w wwww w mw Mir, My m MN mPatented Jan. 20, 1953 FLAME TUBE HAVING TELESCOPING WALLS WITH FLUTEDENDS TO ADMIT AIR Denis McCarthy, and Alan Douglas French Smith,

Derby, England, assignors to Rolls-Royce Limited, Derby, England, aBritish company Application September 2,1948, Serial No. 47,398 In GreatBritain September 10, 194! Claims. 1

This invention relates to gas-turbine engines and more particularlyconcerns combustion equipment for said engines.

A typical gas-turbine engine, as illustrated in Figure 1, comprises acompressor driven by a turbine through a shaft connecting them anddelivering air to combustion equipment 12 in which fuel is burnt in theair and from which the combustion products pass to the turbine to driveit.

In the embodiment illustrated the combustion equipment comprises aseries of combustion chambers 13 disposed in a, ring around the shaftconnecting the turbine with the compressor and each combustion chambercomprises an outer casing or air casing within which a flame tube ofcylindrical or part conical form is positioned so as to be spaced fromthe air casing. In alternative arrangements of combustion equipment theseries of outer casings are replaced by an annular air casing formed byinner and outer substantially cylindrical walls surrounding the shaftinterconnecting the turbine and compressor; in such an arrangement aseries of flame tubes of cylindrical or part conical form may beaccommodated within the annular air casing, or alternatively the flametube itself may be of annular form being constituted by inner and outerflame tube walls spaced respectively from the inner and outer air casingwalls. The present invention is generally applicable to flame tubearrangements, such as those of substantially cylindrical or part conicalform or those providing an annular flame tube space.

In combustion equipment comprising an air casing and flame tubearrangement such as outlined, fuel is delivered into the flame tube andthe air entering the combustion equipment .flow partly as primary airdirectly into the flame tube and partially around it; in additionapertures are usually provided in the wall or walls in the flame tube toallow the air flowing around the flame tubes to pass into them toprovide "secondary or tertiary and possibly additional "primary airsupplies thereto.

One known construction of flame-tube comprises two or more substantiallyfrusto-conical elements disposed end to end and connected together byflanges on them so that the flame-tube had a stepped formation. Airinlet apertures are formed in the walls of the frusto-conical sectionsand in the flanges which extend transversely of the air stream aroundthe flame-tube.

One object of this invention is to provide a flame-tube having rigidityof-structure and also 2 giving rise to improved combustion. Anotherobject of the invention is to reduce the pressure loss attributable tothe passage of air into the interior of the tube.

Another object of the invention is to provide a flame tube having degreeof flexibility, accommodating expansion differences arising from 10- caltemperature variations, and thereby reduce the tendency of theflame-tube to buckle.

Another object of the invention is to provide a construction of flametube which permits flow of the primary and/or secondary and/ or tertiaryair to enter the interior of the flame tube without undue turbulence.

Constructions of flame-tube embodying the invention will now bedescribed by way of example with reference to Figures 2-7 of theaccompanying drawings, of which:

Figure 1 is a side elevational view of a gasturbine engine constructedin accordance with the present invention.

Figure 2 illustrates one construction of combustion equipment with partsbroken away.

Figure 3 is a fragmentary view of part of Fig. 2 to a larger scale.

Figure 4 is a section taken on the line 4-4 in Figure 3.

Figure 5 illustrates another construction of combustion equipment with apart broken away.

Figure 6 is a fragmentary view of part of Figure 5 to a larger scale.

Figure '7 is a section on the line in Figures 5 and 6.

The embodiment of the invention illustrated in Figures 2, 3 and 4 of theaccompanying drawings comprises a domed end-member IQ of knownconstruction with a snout portion ISA through which primary air entersthe flame-tube, and through which a fuel nozzle (not shown) extends toinject fuel into the interior of the flame tube. The flame tubeadditionally comprises an intermediate tubular member 2| with aperaturesfor receiving interconnector tubes and a substantially frusto-conicaltubular discharge member 21 with apertures 26 for the introduction oftertiary air, these members being secured together in line.

The junction between the intermediate member 2| and the frusto-conicalmember 21 (Figure 3 and 4) is arranged to be at the desired point forthe introduction of secondary air into the flame-tube and they aresecured together by tubular, slightly-tapering extensions 22, 24 thereonof a heat-resistant metal, the extension 22 on the intermediate member2| engaging by its 3 end within the extension 24 on the frusto-conica'lmember 27.

The extension 22 of the intermediate member 2| is formed with a numberof circumferentiallyspaced longitudinal inwardly-indented flutes orcorrugations 2.3; so that the-.- extension 22 is; grooved on its outersurface and ridged on its inner surface. The flutes or corrugations 23decrease in depth from the end by which it is:

engaged in the extension 2-ofthe-frusto-conical member 2! to that bywhich it is secured. to the intermediate member 2|.

The extension 24 of thefrusto-conical'member 21 is formed withoppositely-directedflutes or corrugations 28, so that the outer surfacethereof is ridged and the inner surface.- grooved these flutes orcorrugations 28 being likewisecircumferentially-spaced and tapered. sothat when the extensions 22, 24 are interengaged the flutes orcorrugations 23, 28 thereon register with one another and form ducts 29Fof a cross-section tapering slightly from their-inlet.

ends to their outlet ends. The portionsof the extensions 22, 24 betweenthe flutes or corru- 1 gations are in contact and are convenientlysecured together by welding.

It will be clear that by reason of the flutes or corrugations taperingin depth the ducts 29- will be directed inwardly at an angle to the wallof the flame tube and towards the axis thereof in the direction of flowof gases through the flame-tube.

This flow of air is shown generally by the arrows of'Fi'gs. 2 and 3.

The angle, spacing, length, positionandicrosssectional area of theduct-like air inlets'will be selected to give the greatest efficiencyofrmixing of the air and gases;

The embodiment of the invention shown in Figures -7 of the accompanyingdrawings is illustrative of a number of' ways in whichthe' invention canbe applied. shown the flame tube comprises a domed tubular end: member3'! of' known construction with a shout. portion 31A throughwhichprimary air enters the. flame-- tube and through which. a fuel nozzle:(not' shown) extends to spray fuel into theinterior The flame tubeadditionally of the flame tube. comprises two intermediate tubularmembers 69,- M and a fmsto-conical' tubular discharge member 32, thesemembers being secured togetherin line.

As shown in greater detail in Figs. 6 and 'T the domed end-member 37comprises two'tubular members 38, 39 and compressed air from the:

compressor of the engine. has access: between; these two members throughsnout'portiont 37A...

At the junction. of the member: 39' and upstream intermediate member 40(Figures 6 'and' 7), the end-portion of the member 39.xwhich: is.received within the end-portion 44' of, the

upstream intermediate member, is formed with inwardly indented flutes orlongitudinal .corruegations' 43 and the adjacent end-portion 44 of:v

the upstream-intermediate. memhenisacylinderz' Secondary diluting airpassing through these ducts" is thus'introduced into the There are thusprovided between the flutes 43 and the cylindrical end-portion 44duct-like air-passages to introduce cooling air.

The invention is not limited to the details of construction describedabove and a number of modificationsz-will be apparent to' those wellskilled in the art, which may be employed without departing from thescope of the invention.

The flutes or corrugations in accordance with the invention may have anysuitable crosssection,. for example they may be substantiallysemi-circular to form substantially semi-circular-sectioned; or, whenregistering with similar flutes on another part, substantiallycircularsectioned ducts, or they may be such as to form substantiallysquare or rectangular ducts.

It willbeclear moreover, that the fluted or corrugated formation givesmechanical strength to" the flame-tube which is relatively simple tomanufacture.

Moreover,. constructions of flame tube in accordance with the inventioncan be of' the type providing an annular combustion space within anannular'air casin'g'structure. Such a flame tube" may be constituted bysubstantially oylin drical or frusto-conical walls respectively of.greater" and less meanv diameter; and one" orrboth of the walls. maycomprise tubular flame tube' wall members secured: together in line,with the end portion or one member engaged within the end portion of theother member, either orboth of the" tubular members being corrugatedorfluted in a. manner such as described in'relation: to. the.substantially cylindrical: and: part-conical flame tubes described;above; In such annular flame tube: constructions the, duct-like passagesassociated with theouter flame tube wall may be inclinedinthe'directionrof flow towards the aXis-ofthe tubular member, whilst the.passages associated with the-inner flame tube wall may" be inclined inthe direction'of flowaway from; the axis of'the tubular members. In thismannerair introduced bythe duct passages into theinterior of the flametube space will penetrate towards the mean radius of the annulus offlame longitudinal corrugations, asecond flame tubewall-member arrangedin line with said first flame tube-wall-memberand having an integralend'portion engaged within and secured to'saidiintegral end portion ofsaid first wall member; inwardlyindented flutes orlongitudinal oorruga.-tions formed in said integral end'portion. of said second wall member;and. registering with said' outwardly indented .flut'es' or longitudinalcorrugations. to provide between them duct-like: airpassages to theinteriorroftheflame-tube; which air passages. have their inlet ends:facing upstream-.to. thee air-flow exterior to" the flamertube? wall.

2. A- flame-tube as claimed in claim 1 in whichthe inner end-portion hasinwardly indented flutes or. corrugations and. the outer'end portion hasoutwardly indented flutes or corrugationa.

3. In aflame tube for use with the combustion: equipment of a gas:turbine engine,- a pair of tubular flame tube- Wallv members arranged;in;

line with the integral end portion of one member engaged within, andsecured to, the adjacent integral end portion of the other member, eachof which members has its engaging end portion formed with flutes orlongitudinal corrugations to co-operate with the end portion of theother tubular member to provide between them duct-like air passages tothe interior of the flame tube, which air passages have their inlet endsfacin upstream to the air flow exterior to the flame tube wall and havea slightly convergent crosssection throughout their length in thedirection of air flow through them.

4. In a flame tube for use with the combustion equipment of agas-turbine engine, a first tubular flame-tube wall member having anintegral endportion, a second tubular flame-tube wail member arranged inline with said first wall member and having an integral end portionformed with in- Wardly indented flutes or longitudinal corrugations,which end portion is received within said first mentioned integral endportion, engages therewith and is secured thereto, said flutes orlongitudinal corrugations co-operating with said REFERENCES CITED Thefollowing references are of record in the file of this patent: j

UNITED STATES PATENZIS Number Name Date 20 2,268,464 Seippel Dec. 30,1941 2,448,561 Way Sept. 7, 1948 2,510,645 McMahan June 6, 19502,549,858 Sforzini Apr. 24, 1951

